Production of butadiene



Sept. 25, 1945. H. c. HUFFMAN PRonucTIoN oF BTADIENE tiled lawn 1o, 1942 Patented Sept. 25, 1945 UNITED STATES I1 ..1\.T1:-:1\1Ti OFFICE PRODUCTION F -BUIADIENE Hai c. Huffman, Long Beach, Calif., assigner to Union Oil Company of California, Los Angeles, Calif., a corporation of California Application March 10, 1942, Serial No. 434,038

9 claims. (ci. 26o-677) 'Ihe present invention relates to the separation Where X1 and Xa are alkyl groups, unsaturated or recovery of diolens and higher olelns from gases containing the same. More specifically, the

vinvention relates to the treatment of a gas with a selective solvent in order to separate diolens such as butadiene from gases containing butadiene and butenes.

`One of the methods proposed -for producing butadiene 1,3-butadiene) or other dioleilns consists in subjecting mono-olelns such as n-butenes to elevated dehydrogenating temperatures in the presence of a catalyst which results in converting a portionof the butenes into butadiene and hydrogen. The removal of the hydrogen from the products of dehydrogenation may be easily` accomplished by well known rectification methods.

However, the separation of the unconverted nbutenes from the butadiene by rectication is exceedingly diillcult, impractical and uneconomical due to the fact that these components boil so close together.

It is an object of my invention to provide an economical and practical process for separating dioleiins from the oleins and/or saturated hydrocarbons boiling substantially in the same temperature range as said diolens. Y

Another object of my invention resides inthe use of certain solvents for selectively extracting dioleilns from mixtures containing the same.

Other objects, features and advantages of my invention will be apparent as the description of my process proceeds.

'Ihe solvents which I have discovered as useful for extracting butadiene and other diolens from gases containing the same are those compounds of the general type in which one or more carbOXyl groups have been substitutedfor hydrogen in thio-ethers, such as alkyl suldes or thiophanes. More specifically, I prefer to use ethyl thioglycolic acid and/or its homologs, of which I prefer to use a mixture resulting from the acid hydrolysis of the reaction product oimethyl, ethyl, propyl, butyl and amyl sodiomercaptides with sodium chloroacetate. Such a mixture of sodiomercaptides is usually available as renery waste-alkali liquors which have been used to remove mercaptans from gasoline distillates. Ethyl thioglycolic acid (CHaCHz-S-CHz-COZH) has a. boiling point of about 123 C. at 15 mm. Hg pressure and a .specific gravity of 1.148 at'26" C.

Solvents which may also be used are thioglycolic acids in which the alkyl group may be substituted by aryl groups or aralkyl groups. The invention also includes the use of RS-substituted carboxylic acids of the following type:

Rs\ i A vXi--c-r-coon Y radicals derivedi'rom alkyl groups by loss of hydrogen, aralkyl groups, hydrogen, carbocyclic rings, heterocyclic rings or RS groups the same or different from the RS-group shown and in which R represents an alkyl, aralkyl, carbocyclic orheterocyclic group, or an unsaturated radical derived from an alkyl group by loss of hydrogen and Y represents (CH2M where n=0 or an integer which may be as high as 5 or higher.

In other words, the invention maybe said to reside in the use as extraction solvents forthe separation of oleflns described herein, which solvents comprise RS-substituted carboxylic acids containing one or more carboxyl groups, as for example, the Its-substituted mono-carboxylic acids such as ethanoic, propanoic, butanoic, etc. acids or RS-sub'stituted poly-carboxylic acids, such as succinic, adipic, etc., acids. Examples of such RS-substituted carboxylic acids include ethylthioethanoic (ethyl thioglycolic) acid, 3-prolpylthiopropanoic acid, 4-cyclohexylthiobutanoic acid, 2-methyl-3-phenylthiopropanoic acid, 2-isopropylthio3 (Z-pyridyIthlo) -butanoic acid, and 2-propenylthio-4- (p-tolyl) -pentanoic acid.

The following description of my invention as taken from the accompanying drawing which represents a diagrammatical view of apparatus adapted to carry out my invention may serve to aid in a better understanding of my invention.

In the drawing, the solvent, such as ethyl thioglycolic acid, is withdrawn from-storage tank l0 via line Il controlled by valve `l2 and is pumped by pump I4. through cooler I5 Where the solvent iscooled to the desired temperature of extraction. The cooled solvent is then passed via line I6 and is introduced into the top of the extraction column ll which is provided with suitable contacti ing elements such as raschig rings, broken checkerwork, bubble plates, etc., in order to obtain intimate contact with the gas to be extracted. The solvent flows downwardly in the extraction column countercurrently to the upwardly flowing gas to be described.

The gas to be extracted, such as one consisting predominantlyof butadiene and butene, coming into the system via line 20 is compressed bycompressor 2l, cooled to the temperature of extraction in cooler 22 and passed via line 23 into the bottom of the extraction column.

In theV extraction column, the solvent selectively extracts the butadiene, leaving the butenes and other gases, such as iso-butene and butane free to be 'removed from the top of the column via line 24 controlled by valve 25. Valve 25 together with compressor 2| controls the pressure in the extraction column. lDuring extraction,

butadiene. recovered. in theprocess may be re- A cycled to the extractioncolumn to act as reflux during the extraction. The recycled butadiene atmospheric pressure.

as a liquid.

The solvent containing the extracted butadiene is withdrawn from the bottom of the extraction column via line 26 controlled by valve 21 and is pumped by pump 28 and line 29 into an evaporator 30 which is provided with a heating coil 3l through which steam or other heated medium may be circulated to. heat the solvent and evaporate the butadiene. The vaporized butadiene is withdrawn from the top of the evaporator via line 32 controlled by valve 33 and is passed to asuitable storage tank. Part of this butadiene is preferably' recycled to the extraction column at a point near the center of the column. If the extraction is effected while the gas is in the liquid phase as explained hereinafter, it is preferable to liquefy the butadiene by compression and cooling before recycling it to the column. If the extraction is carried out on a gaseous mixture, the recycled butadiene may be either in the gaseous or liquid state.

The solvent free from the butadiene is withdrawn via line 34 controlled by valve 35 and is pumped by pump 36 through line 31 into storage tank I for further use as described above.

The extraction of the Ibutadiene from the remaining gases may be carried out either while the gas is in the vapor state or while the gas is in the liquid state. In the latter case, the incoming gas in line 20 is compressed sufnciently to liquefy the gas when cooled in cooler 22. The temperature of extraction may vary between 30 and 100 C.Y while the pressure may Vary between atmospheric and superatmospheric pressures of 200 pounds per square inch.. I prefer to effect the extraction at room temperature or below while the gas is in the vapor state and either at atmospheric or super- When the extraction is under superatmospheric pressure, the removal of the extracted butadiene in evaporator 30 may be accomplished or aided by releasing the atmospheric pressure.

pressure to While the foregoing description of my invention has been made with particular emphasis in the separation of butadiene from butenes, itwill be observed that these solvents are' also useful for separating other diolens such as pentadiene from' other hydrocarbons such as amylene. Nor is the invention to be considered restricted to the separation of dolefins from mono-oleflns4 since these solvents will selectively extract the dioleiins from saturated hydrocarbons .such as butane, pentane, etc. These solvents are also capable of extracting dioleiins from tertiary mono-olefins. Hence, diolens may be extracted from mixtures containing also tertiaryv mono-olei-lns, straight chain mono-olefins and saturated hydrocarbons.

These solvents are alsocapable of selectively extracting tertiary mono-olens, such as isobutylene from-straight chain mono-olens such as butylene and also saturated hydrocarbons, such as butane from said straight chain mono-olens. The recovery ,of tertiary mono-oleflns. such as isobutylene is of great technical value since these may be hydrated to form tertiary alcohols which phenols to yield valuable tertiary alkyl phenols or to alkylate isoparaflins to give high octane aviation alkylate. Polymerization of some tertiary mono-olens such as isobutylene to yield4 high octane gasoline may be brought about by of 5 parts by weight of beryllia, 5 parts of chromithe use lof sulfuric acid, heat or other agents.

technical value. l

The separate recovery of the straight chain mono-olens from mixtures containing ,the tertiary mono-olefins is also of great technical value in the alkylation field. For example, n-butylenes have been found to give longer catalyst life and a better product when used in the alkylation of isoparaflins to yield aviation alkylate than does the tertiary mono-olefin or isobutylene.

Of course, in separating the various components disclosed above, the conditions of extraction, i. e., temperature, pressure and amount of solvent, will vary with the particular mixture to'be extracted.

The presence of water in the solvent or during the extraction decreases the solubility of the solvent for various hydrocarbons included above.

'For example, the following table lists thesolubilities at 25 C. of various hydrocarbons in ethyl thivoglycolic acid of various concentrations:

Solubility (ml. gas/ml. solvent) Compound 100% acid acid acid acid aci acid 10% 20% 307 40% 50% nio nio Hi H20 H,

1, -butadiene 23. 7 1G. 1 12. 1 10. 6 6. 5 5. 8 l-butylene 0. 6 1. 9 3. 6 4. 4 3. 8 1. 5 2-butyleiie (cis and trans) 2. 0 2. 0 2. 4 5.0 3. 3 2. 5 Iso-butylene 11. 3 8. 8 7. 6 5. 2 4. J 2. 7 n-butane A i3. 5 7. 1 3. 9 3. l l 1. 9 1.6

Thus, in the foregoing table, 1,3-butadiene is about 39.5 times more soluble in 100% strength acid -than 1butylene and 11.8 times more soluble than Z-butylene (cis and trans). Hence, the foregoing table illustrates the feasibility and desirability of operating with substantially pure solvents. However, since the respective solubilities of the various components are somewhat different even in the presence of water, a separation may be .made between those components having relative- Example 1 A gaseous mixture composed of approximately 32 parts by volume of 1,3butadiene,65 parts of n-butenes and 3 parts of butane and produced by dehydrogenation of n-butenes at a temperature of 575 C. in the presence of a catalyst composed um sesquioxide and parts of activated alumina., was countercurrently passed in contact with ethyl thioglycolic acid. Approximately 20 parts of the gaseous mixture were contacted per volume of the acid at a temperature of 27 C. and atmospheric pressure. The unabsorbed gas was separated from the solution of acid and the latter was then heated to 50 C. to remove the 1,3-butadiene extracted by the acid.

The gas separated from the solvent consisted of approximately 98% of 1,3-butadiene containing a small amount of butane and was recovered practically quantitatively.

:sample z A gaseous mixture as in Exampley 1 was liqueiled and cooled and was then extracted with an equal volume of propyl thio-glycciic acid at a temperature of approximately 20 C. and at a pressure of approximately three atmospheres. The extraction was accomplished by mixing the acid andthe liqueiied gas in a pressure bomb and then allowing vthe mixture tov stratify into two layers,

i. e., a lower layer of the acid containing dissolved butadiene and a n upper layer ofthe unextracttrd4 ance withvthe method employed in Example 1. The solution of solvent and isobutylene was distilled at 50 C. which resulted i'n the removal of the dissolved isobutylene !rom the solvent.A The recovered isobutylenefraction was substantially pure. l j

Example 4 The same procedure as in Example 1 was em- DlOyed to treat amixture composed of equal vol- ,umes oi' butane and butenes with .the result that the solvent extracted substantially all of he bi1- tane from the gaseous mixture.

'I'he foregoing description oi' my invention is not to be taken as limiting the invention which may include any method which accomplishes the same Vwithin the scope ci' the appended claims.

I claim: i l. A process for separation. oi' dioleilns fro hydrocarbon mixtures containing the same and 'boiling substantially inthe same temperature frange. which comprises extracting 'said hydrocarbon` mixture ywith a compound having the general formula i ns\ xl7c-Y-Pcoon where X1 and X: are selected from the group consisting of alkyl groups, unsaturated radicals derived from alkyll groups by loss of hydrogen, aralkyl groups, hydrogen, carbocyclic rings, heterocyclic rings and RS groups the same or different from-the RS group shown and in which R'is selected from the group consisting of an alkyl group, an aralkyl group. a carbocyclic group, a heterocyclic group. and an unsaturated radical derived from an alkyl group by loss of hydrogen and Y represents (CH2). where n =0 or an integer and thereby forming a solution ot said compound and said dioleilnsgand separating said solution from unextracted hydrocarbons.

2. A process for lthe separation of tertiary mono-oleilns 'from a hydrocarbon mixture containing teritiary mono-olefins and other \hydro carbons and `boiling substantially in the same ing the general formula xic-Y-c o on waere x1 and x: are selected from the group consisting of alkyl groups, unsaturated radicals derived from alkyl groups by loss oi hydrogen, aralykyl groups, hydrogen, carbocyclic rings, heterocyclic rings and RS groups the same or dinerent from the RS group shown and in which R is selected from the group consisting of an alkyl group, an aralkyl group, a carbocyclicgroup,

-. a heterocyclic group, and are unsaturated radical derived from an alkyl group byloss of hy- 'drogen and Y represents (Cima where n=0 or an integer thereby forming a solution of said compound and said tertiary .mono-olens and separating said solution from unextracted hydrocarbons.

3. A process for the separation of butadiene from a hydrocarbon mixture containing .butadiene and boiling substantially in the same temperature range. which comprises extracting said hydrocarbon mixture with a compound having the general formula xi-c-Y-coon where X1 and X: are selected from -the group consisting o! alkyl groups, unsaturated radicals derived from alkyl groups by loss of hydrogen, aralkyl groups, hydrogen, carbocyclic rings.

heterccyclic rings and RS groups the same or different from the RS group shown and in which R is selected from the group consisting of an alkyl group, an aralkyl group, a carbocyclic group, a heterocyclic group, and an unsaturated radical derived from an alkyl group by loss of hydrogen and Y represent (CH2M where n=0 or an integer thereby forming a solution of said compound and butadiene and separating said solution from the unextracted hydrocarbons.

4. A process i'or the separation of butadieneA from 'a hydrocarbonmixture containing butadiene and boiling substantially in the same temperature range, which comprises extracting said hydrocarbon mixture with ethyl thioglycolic acid, thereby forming a solution of said ethyl thioglycolic acid and butadiene and separating said solution from the unextracted hydrocarbons.

5. A process according to claim l in which the selective solvent comprises a major proportion of 'ethyl thioglycolic acid and a minor proportion of water.

6. A process for the separation of isobutylene from a hydrocarbon mixture containing the same and boiling substantially in the same temperature range which comprises extracting said mixture with a selective solvent comprising ethyl thioglycolic acid thereby forming a solution of said isobutylene and said selective solvent, and

separating said solution from yunextracted hyve carbon atoms.

. HALl C. HUFFMAN. 

